1. Field of the Invention
The present invention relates generally to integrated optical signal communicating devices utilizing semiconductor bodies and more particularly to such devices capable of maintaining optimum light communication capability after exposure to ionizing and neutron radiation.
2. Description of the Prior Art
The field of integrated optics or thin-film optoelectronics--thin film optical devices so small that they can be placed one next to the other on a single substrate-offers great promise in signal processing and communication. Active optical systems have been proposed requiring monolithic integration of a semiconductor light-generating device, such as an electro-luminescent diode or laser, a waveguide, a detector and perhaps a modulator on the same clip. Much research in optical-component integration involves development of fabrication techniques for gallium arsenide, since it is most suitable for electro-luminescent diodes and photo detectors, and the large electro-optic effect in gallium arsenide allows efficient phase modulation of gallium arsenide thin films used as waveguides.
However, the electro-optical characteristics of gallium arsenide, such as quantum or light-emitting efficiency, absorption coefficients, and index of refraction are degraded by the ionization which occurs under the influence of gamma and neutron radiation. In order to prevent too great an impairment of the function of circuits equipped with gallium arsenide integrated optical signal communicating devices in their application, say, in earth satellites and space vehicles, the devices should have a radiation resistance, i.e., radiation hardening, as high as possible.